Drive device for a finger prosthesis

ABSTRACT

Drive device ( 1 ) for a finger prosthesis ( 2 ) of substantially natural size designed to bend the finger prosthesis ( 2 ) about a shaft (A) relative to a fixing ( 3 ) e.g. in a human or artificial metacarpus ( 4 ). The drive device ( 1 ) comprises a motor ( 6 ) which can be connected to an energy source e.g. a battery, and a transmission (5, 7, 8) intended to transform a force from the motor ( 6 ) to the finger prosthesis ( 2 ) to perform the movement. The motor ( 6 ) and transmission ( 5, 7, 8 ) are placed in the finger prosthesis ( 2 ) so that the bending shaft (A) is contained in the finger prosthesis ( 2 ) or in its extension at the fixing ( 3 ).

TECHNICAL FIELD

The present invention concerns a device for operating the movement of afinger prosthesis. The finger prosthesis has a natural size and isintended to be attached to a metacarpus prosthesis or a human hand. Thefinger prosthesis and metacarpus prosthesis are intended to replace acorresponding lost human body part.

BACKGROUND OF THE INVENTION AND PROBLEM

When a hand or metacarpus and fingers are lost or amputated, they can bereplaced by a corresponding prosthesis. This means a loss of afunctioning body part with realistic appearance and a movement patternwhich a prosthesis must simulate.

The prosthesis to replace the lost body part should be simple to repairand also have a cost-effective construction so that e.g. the supply ofspare parts can be improved.

Some known finger prostheses have a drive device with means fortransmitting energy from a motor arranged at the wrist to the fingerprosthesis, which means e.g. contain wires to achieve a bending of thefingers. On failure of a finger prosthesis the fault must first belocated in the wrist, finger prosthesis or transfer means, where uponthe part concerned must be repaired or replaced. Arranging the motorsand drive elements in an artificial metacarpus reduces the possibilityof arranging other organs therein.

The finger prosthesis must also have as natural a bending movement aspossible and be gentle towards a prosthesis cover consisting of anelastic material and arranged finally over the finger prosthesis tosimulate human skin.

Specification U.S. Pat. No. 5,888,246 discloses a device for bending afinger prosthesis. The device has a motor and drive/gear elementsdesigned to bend the entire finger prosthesis. The text also describes aworm gear to transform the motor rotation into the finger prosthesismovement.

OBJECT OF THE INVENTION AND SOLUTION OF THE PROBLEM

The object of the invention is to solve one or more of the aboveproblems.

This is achieved with a device according to claim 1.

By integrating a drive device, comprising a motor and transmissionintended to transform the motor movement into finger movement, in afinger prosthesis designed to bend the finger prosthesis about a shaftin relation to a fixing, e.g. in a metacarpus prosthesis or human hand,in a movement direction from an extended position towards a palm and outagain to the extended position, a finger prosthesis with substantiallynatural size is obtained which is easy to replace and allows asimplified repair of the finger prostheses. The motor can be connectedto an energy source e.g. a battery.

Furthermore by placing the motor and transmission in the fingerprosthesis, importantly space is created at other points e.g. in ametacarpus prosthesis, which means that the metacarpus prosthesis e.g.can be made smaller and/or contain other equipment e.g. control devicesor batteries.

Furthermore by dividing the finger prosthesis into two parts pivotableagainst each other and coupling the movement of these parts together, asimulation of a human finger in appearance and movement is achieved.

DESCRIPTION OF THE DRAWINGS

The invention will be described further in an embodiment example withreference to the figures as follows.

FIG. 1 shows a diagrammatic cross-section sketch from the side of adrive device according to the invention for a finger prosthesis.

FIG. 2 shows a diagrammatic sketch of an angled gear according to theinvention for a finger prosthesis.

FIG. 3 shows a diagrammatic cross-section sketch from the side of adrive device according to the invention with a pantograph rod for afinger prosthesis in extended position.

FIG. 4 shows a diagrammatic cross-section sketch from the side of adrive device according to the invention with a pantograph rod for afinger prosthesis in the bent position.

FIG. 5 shows a diagrammatic sketch of a drive device according to theinvention in a finger prosthesis attached to a hand prosthesis.

FIG. 6 shows a hand prosthesis according to FIG. 5 b with the fingerprostheses bent towards the palm.

FIG. 7 shows a diagrammatic sketch, in a view towards a palm, of a drivedevice according to the invention in a finger prosthesis fastened to ahand prosthesis.

DESCRIPTION OF EMBODIMENT EXAMPLE

A drive device for bending a finger prosthesis is referred to generallyas 1, where the finger prosthesis is referred to as 2. A fixing 3 isdesigned to attach the finger prosthesis to a human or artificialmetacarpus 4. Substantially the entire finger prosthesis is designed tobend relative to the fixing 3 to simulate a human finger movement.Furthermore the finger prosthesis has a first part 2 a and a second part2 b which are connected at a finger joint 2 c so that the parts can movein relation to each other to further simulate a human finger movement.The finger prosthesis 2 is intended to bend about a shaft A placed atthe fixing 3. A transmission 5 contains a gearbox 5 b and an angled gear5 a. The angled gear 5 a is arranged at shaft A and preferably has twobevel gear wheels 7, 8, of which the first gear wheel 7 has teeth atleast partly about shaft A, and the other gear wheel 8 has teeth aroundan outgoing shaft B from gearbox 5 b. The first gear wheel 7 in thepreferred embodiment is designed as a bevel gear wheel describing a partsmaller than a complete rotation. As the finger is to be turned/bentaround shaft A through 70 to 100 degrees, the gear wheel 7 describesaround 120 degrees. Shafts A, B are arranged substantially in the sameplane but in an alternative embodiment of the angled gear 5 a, thesecond gear wheel 8 can be arranged slightly offset along the edge ofthe first gear wheel 7, e.g. by means of a hypold gear, where the planesof the shafts do not lie in the same plane but close to each other. Atgearbox 5 b is also a motor 6. The motor 6 and gearbox 5 b are mountedtogether and housed in the finger prosthesis 2 between shaft A and thefinger joint 2 c. The gearbox 5 b is advantageously of the trochoidtype. The motor 6 is preferably an electric motor and can therefore beconnected by means of a power supply lead to a battery. The centralshaft of the motor coincides substantially with a central axis C for thefinger which extends in the linear centre and along the extent of thefinger. The gearbox 5 b and the two bevel gear wheels 7, 8 are designedto transform the energy of motor 6 into finger movement and hence forcein the finger prosthesis. As the finger prosthesis 2 contains the motor6 and the two bevel gear wheels 7, 8, the finger prosthesis 2 canquickly be detached from e.g. the metacarpus prosthesis 4 by opening thefixing and releasing an electrical contact 12 for the power supply, thussimplifying e.g. exchange of finger 2 for repair.

The finger prosthesis 2 is substantially of natural size and is designedto give a natural movement pattern. Thus the finger prosthesis 2,referred to below in the description as the finger 2, is formed from asubstantially circular tube, preferably of a light and strong materiale.g. aluminium or reinforced plastic. Furthermore both shaft A andfinger joint 2 c are arranged substantially in the centre of finger 2 ata central axis C or in an alternative embodiment at least within ±15 mmfrom the centre axis C to give a natural movement pattern. On use,finger 2 usually has a skin-simulating prosthesis cover (not shown). Byarranging finger joint 2 c and/or shaft A substantially in the middle ofthe hollow tube or its extension, advantageously on finger movement theprosthesis cover stretches on the outside of the joint or fastening 3i.e. at the knuckle and the cover is compressed on the inside i.e. onthe side of finger 2 which on bending is on the inside on bendingdirection I. This reduces the maximum load on the prosthesis cover.

A pantograph rod 9 is arranged preferably on each side of the fingerprosthesis, see FIGS. 3 and 4. The pantograph rod 9 is attachedpivotably at the first end 9 a to the fixing 3 of the prosthesis fingerat a point 10 a which does not move with the prosthesis on bending. Theother end 9 b of the pantograph rod 9 is pivotably connected to theother part 2 b of the finger prosthesis at a point on this part 2 blocated before the finger joint on the inside viewed in the benddirection I for the finger prosthesis towards an artificial or humanpalm. On extension of the prosthesis finger 2 therefore the pantographrod 9 has a compressive effect and presses the other finger prosthesispart 2 b towards an extended position, see FIG. 5 b. The bend movementbetween the first and second prosthesis parts 2 a and 2 b is thuscontrolled by the bending movement between the first part 2 a of thefinger prosthesis relative to fixing 3, see FIGS. 3 to 6. Operating boththese bending movements at the same time with a common motor 6, gearbox5 b and angle gear gives a simple and robust prosthesis designed tosimulate a human finger and its movement. In the preferred embodimentthe finger prosthesis 2 has two pantograph rods which are arranged oneither side of the finger prosthesis 2.

The finger prostheses as above can be arranged next to each other e.g.to replace the lost human index, middle and ring fingers as shown inFIGS. 5 b and 6.

The invention should not be regarded as limited to the examplesdescribed above but can vary within the scope of the claims.

List of References

1 drive device

2 finger prosthesis

2 a first part of finger prosthesis

2 b second part of finger prosthesis

3 fixing

4 metacarpus

4 a part of metacarpus

5 gearbox

6 motor

7 first gear wheel

8 second gear wheel

9 pantograph rod

9 a first part of pantograph rod

9 b second part of pantograph rod

10 a fixing point at fixing

10 b fixing point at other prosthesis parts

11 palm

12 contact

I Bend angle

A Bend shaft

B Gearbox shaft

C Centre axis

1. A drive device with a finger prosthesis of substantially natural sizedesigned to bend a finger prosthesis about a shaft in relation to afixing at a human or artificial metacarpus at a bending angle from anextended position towards a palm and out again to the extended position,where the drive device comprises a motor which can be connected to anenergy source e.g. a battery, and a transmission designed to transformpower from the motor to the finger prosthesis to perform the bending,wherein the motor and the transmission are placed in the fingerprosthesis so that the bending shaft is contained in the fingerprosthesis or its extension at the fastening.
 2. The drive deviceaccording to claim 1, wherein the bending shaft is arranged within 15 mmfrom a center axis which extends along the center of the fingerprosthesis.
 3. The drive device according to claim 1, wherein thetransmission a first drive wheel connected with the motor and a seconddrive wheel connected with the fastening, which drive wheel is designedunder co-operation with others to transfer the force from the motor tothe finger prosthesis to perform the movement, where the drive wheelsare arranged on shafts which lie substantially in the same plane.
 4. Thedrive device according to claim 1, wherein the finger prosthesiscomprises a first and a second prosthesis part which are connectedtogether by articulation, that the transmission furthermore comprisespivoting means to pivot the second finger prosthesis part relative tothe first finger prosthesis part in towards the palm.
 5. The drivedevice according to claim 4, wherein the pivoting means comprise apantograph rod which has a first articulated fastening at the fingerprosthesis fixing and extends past the first part of the fingerprosthesis and has a second articulated fixing in the second part of thefinger prosthesis at a point on this part which, on tension in thepantograph rod, causes bending in towards the palm.
 6. The drive deviceaccording to claim 1, wherein the motor is an electric motor and thatthe energy source is arranged separately from the finger prosthesis e.g.in the metacarpus, that at the fixing is a contact for dividing thepower supply arranged between the motor and the energy source.